1. Field of the Invention
The present invention generally relates to an optical semiconductor device utilizing an optical semiconductor chip such as an LED chip.
2. Description of the Related Art
A light emitting diode (LED) has advantages such as small power consumption, small size and long lifetime. Therefore, an optical semiconductor device utilizing an LED chip is widely used as a light source in various fields. Examples of such optical semiconductor device are disclosed in JP-A-11-345912 and JP-A-2000-183407. In these prior art devices, a convex lens or a reflector is provided to enhance the directivity of light or increase the brightness.
FIG. 7 shows an example of optical semiconductor device as a related art. In the illustrated semiconductor device B, an LED chip 102 mounted on a substrate 101 is covered with a light permeable member 103. The light permeable member 103 has an upper portion formed with a convex lens 131. The light permeable member 103 is surrounded by a reflector 104. The reflector 104 has an inclined surface (reflecting surface) 141 for reflecting light.
As shown in FIG. 7, the light emitted from the LED chip 102 partially passes through the convex lens 131 and is partially reflected by the reflecting surface 141 of the reflector 104. The light passed through the convex lens 131 travels as a beam of light which is parallel to the axis of the lens 131. The light reflected by the reflecting surface 141 of the reflector 104 is directed upward.
With such a structure, the light emitted from the LED chip 102 can be directed generally in the same direction, so that the illumination target region can be illuminated properly. However, the optical semiconductor device B has the following problems.
The convex lens 131 of the optical semiconductor device B projects upward beyond the upper surface of the reflector 104. Therefore, the outside dimension of the optical semiconductor device B is larger than an optical semiconductor device which does not include a convex lens.
For example, the optical semiconductor device B is used as a light source of a back light of a liquid crystal display incorporated in a cellular phone. In this case, as shown in FIG. 8, the optical semiconductor device B is disposed to face a side surface of a light guide panel 161 arranged at the back of a liquid crystal panel 160. However, since the dimension of the optical semiconductor device B increases by as much as the projecting amount of the convex lens 131 as noted above, the size of cellular phone cannot be reduced sufficiently. Further, in the optical semiconductor device B, the lens 131 is liable to be damaged in carrying the device or mounting the device to a predetermined portion.